The present invention relates to a micro surface measuring apparatus preferably used for measuring a three-dimensional configuration of a machine component in the submillimeter order. For example, this measuring apparatus is applicable to the microstructural measurement for the micro machine parts as well as measurement of an inner surface configuration for the fuel injector nozzles employed in the internal combustion engines or the ink jet nozzles of various printers. More specifically, the present invention relates to a contact-type micro surface configuration measuring apparatus using a probe directly brought into contact with an objective surface to be measured, and also relates to a related method for manufacturing the probe.
The unexamined Japanese patent application No. Kokai 5-264214 or 6-323845 discloses a conventional contact-type micro surface measuring apparatus which is capable of inserting a probe into a narrow or deep portion in a microstructural body or member. Its detailed structure will be explained, hereinafter.
FIG. 15 shows a first conventional arrangement represented by the unexamined Japanese patent application No. Kokai 5-264214. A probe 101, when actuated by an actuator 102, oscillates in a direction shown by an arrow. The probe 101 is placed closely to a measuring object 103. The measuring object 103 is mounted on an X stage 105 which is shiftable in the X-axis direction. The X stage 105 is mounted on a Z stage 104 which is shiftable in the Z-axis direction. The Z stage 104 is connected to and driven by a Z-axis feed mechanism 106. The X stage 105 is connected to and driven by an X-axis feed mechanism 107. A duty cycle measuring device 108, interposed between the probe 101 and the measuring object 103, measures the duty cycle. A computer 109 controls the Z-axis feed mechanism 106, the X-axis feed mechanism 107, and the duty cycle measuring device 108.
According to this arrangement, the actuator 102 causes the probe 101 to oscillate at a predetermined position with a constant amplitude as shown by the arrow in FIG. 15. Electrical conduction between the probe 101 and the measuring object 103 is detectable as short-circuit current measured when a DC voltage is applied between the probe 101 and the measuring object 103. The duty cycle measuring device 108 detects the ratio of a conductive duration to the oscillation period.
For example, when the oscillating probe 101 exceeds a certain displacement xe2x80x9csxe2x80x9d as shown in FIG. 16A, the electrically conductive condition is maintained between the probe 101 and the measuring object 103 as shown in FIG. 16B. FIG. 17 shows a relationship between the measured duty cycle and the relative distance between the probe 101 and the measuring object 103. By recording the duty cycle in this manner, the Z-axis feed mechanism 106 is driven to detect the surface configuration of the measuring object 103.
As understood from FIG. 17, the obtained relationship is not completely proportional. It is, however, possible to improve the proportionality when the sine wave in the oscillation of the probe 101 is changed to a triangular wave. When the undulation on the objective surface of the measuring object 103 exceeds the amplitude of the probe 101, the X-axis drive mechanism 107 is controlled to re-position the measuring object 103 for the measurement of the surface configuration of the measuring object 103.
A second conventional arrangement is based on the AFM (scanning-type atomic force microscope) techniques which have been rapidly developed and applicable to the micro configuration measurement. The unexamined Japanese patent application No. Kokai 6-323845 discloses an advanced AFM probe having a simplified structure and applicable to the micro configuration measurement for mechanical parts, whereas many of conventional AFM systems require a large-scale optical system to detect an interatomic force acting on the probe.
FIGS. 18 and 19 show the schematic arrangement of the second conventional arrangement. A probe 201 is made of an elastic filmy plate of SiO2 or the like whose size is 200xcx9c300 xcexcm in length, 40xcx9c50 xcexcm in width, and 1.8 xcexcm in thickness. A pointed tip 201a, made of ZnO whiskers, is bonded at the distal end of the probe 201.
A piezoelectric film 202b, made of ZnO, is sandwiched between electrodes 202a and 202c and located on the surface of the probe 201. The probe 201 is provided on the surface of a silicon wafer 203. FIG. 19 shows a practical arrangement of a measuring apparatus using the above-described probe 201. A sample 206 is placed on a base body 204 via a Z-axis shift mechanism 205. The probe 201 is attached to the base body 204 via an XYZ piezoelectric scanner 207 and a piezoelectric plate 208 as shown in the drawing.
According to this practical arrangement, the piezoelectric plate 208 causes the probe 201 to oscillate at its resonance frequency. The sample 206 approaches the pointed tip 201a of the probe 201 so closely that the oscillating condition of the probe 201 is significantly influenced by an interatomic force. A distortion signal, detectable by the piezoelectric film 202b, has the amplitude and phase variable in response to the detected oscillation. The position of the XYZ piezoelectric scanner 207 in the Z-axis direction is controlled so as to maintain the changes in the amplitude and phase of the distortion signal, thereby detecting the surface configuration of the sample 206.
The AFM detection mode is roughly classified into a contact mode (tapping mode) and a non-contact mode, as introduced in the journal of society of precision engineering, Vol. 62, No. 3, 1996, pp.345xcx9c350. The non-contact mode is a measurement mode preferable in that no damage is given to the surface of the sample. However, an absorbing layer, such as water on the sample surface, gives adverse influence in this measurement mode. Thus, the measurement is performed in the vacuum.
On the other hand, the tapping mode is free from such problems derived from the absorbing layer. The AFM measurement according to this mode is generally performed in the air and is, therefore, applicable to the micro configuration measurement for many of mechanical parts. FIGS. 20A and 20B cooperatively show the principle of the contact detection in the tapping mode.
In the condition shown in FIG. 20A, the piezoelectric film 202b detects a distortion waveform 211 of the probe 201 whose phase is delayed 90xc2x0 with respect to the exciting waveform 210 of the probe 201. In the condition shown in FIG. 20B, the pointed tip 201a is brought into contact with the sample 206. In such contact condition, the oscillation of the probe 201 is restricted so as to cause the distortion waveform 211 varied in the amplitude. The configuration of the sample 206 is thus measured based on the amplitude change of the distortion waveform 211. Although not shown in the drawing, it will be possible to detect the configuration of the sample 206 based on the phase change in addition to the amplitude change.
The above-described two conventional measurements are applicable to the configuration measurement of a nozzle hole or a micro groove. However, they have the following problems.
According to the former case represented by the unexamined Japanese patent application No. Kokai 5-264214, the detection of contact condition basically relies on the electrical conduction between the probe 101 and the measuring object 103. Thus, this measuring method is not applicable to the non-conductive members. Furthermore, even if the measuring object is electrically conductive, the measurement accuracy will be deteriorated by oxide films covering the surface or dusts on the surface.
On the other hand, the latter case represented by the unexamined Japanese patent application No. Kokai 6-323845 has the capability of detecting the internal micro configuration regardless of conductiveness of the measuring object.
However, measuring objects are not limited to the ordinary AFM measuring objects, such as semiconductor surfaces or vacuum processed samples. For example, oily or dusty parts will contaminate the AFM probe 201 and render the measurement useless. Hard or rigid parts will abrade the probe 201. The measuring object, when its surface has large undulation, may damage the probe.
In view of the foregoing problems encountered in the prior art, the present invention has an object to provide a surface configuration measuring apparatus capable of measuring the micro surface configuration of mechanical parts, and also has an object to provide a method for manufacturing the probe used in the surface configuration measuring apparatus.
In order to accomplish the above-described and other related objects, the present invention provides a micro surface measuring apparatus for measuring the configuration of an objective surface. The apparatus comprises a probe having a cantilever structure, an oscillating means for oscillating the probe at or near its resonance frequency, a distortion detecting means for detecting a distortion amount of the probe, a positioning means for adjusting the position of the probe in an oscillating direction so as to stabilize the distortion amount at a constant value, and a shifting means for adjusting the mutual position between the probe and the objective surface.
More specifically, by using the micro electric discharge machining, a cemented carbide (sintered hard alloy) is configured into a probe having a cantilever structure with a pointed tip for measuring the configuration of a measuring object. A piezoelectric ceramic, supporting this probe, causes the probe to oscillate at or near its resonance frequency. When the oscillating pointed tip is brought into contact with the surface of the measuring object, the oscillating probe has the amplitude and phase varying in accordance with the degree of the contact. A piezoelectric ceramic, provided on the probe, produces a distortion signal reflecting the distortion derived from the contact between the probe and the measuring object. The servo positioning of the probe is performed so as to stabilize at least one of the amplitude and the phase of the distortion signal.
The probe is shifted along the surface of the measuring object while maintaining a relative distance between the probe and the measuring object. Thus, the probe moves along the surface of the measuring object. It becomes possible to measure the configuration of the measuring object.
In other words, the present invention realizes a micro surface configuration measuring apparatus capable of stably measuring the surface of a measuring object regardless of its conductiveness, not adversely influenced by the oxide film or dusts on the surface, with a probe which is highly resistive in abrasion, highly stable in shape, and highly durable in corrosion.
The present invention provides a micro surface measuring apparatus for measuring the configuration of an objective surface, the apparatus comprising a probe having a cantilever structure, oscillating means for oscillating the probe at or near its resonance frequency, distortion detecting means for detecting a distortion amount of the probe, positioning means for adjusting the position of the probe in an oscillating direction so as to stabilize the distortion amount at a constant value, and shifting means for adjusting the mutual position between the probe and the objective surface.
With this arrangement, it becomes possible to measure the configuration of the measuring object regardless of its conductiveness, without being adversely influenced by the oxide film or dusts on the surface.
It is preferable that the probe has a pointed tip measuring the configuration of the objective surface and made of a conductive member which is high in hardness.
Furthermore, it is preferable that the probe is made of a cemented carbide which is highly resistive in abrasion, highly stable in shape, and highly durable in corrosion. The configuration measurement for mechanical parts can be stably performed under actual environments.
Furthermore, it is preferable that the probe is partially or entirely made of a diamond or BN (boron nitride) sintered material which is harder than the cemented carbide. This is effective to enhance the resistivity in abrasion and the stability in shape. The configuration measurement for mechanical parts can be stably performed under actual environments.
Furthermore, it is preferable that the probe is manufactured by a micro electric discharge machining. It becomes possible to flexibly form the probe in various shape.
Furthermore, it is preferable that a deteriorated layer formed during the micro electric discharge machining is removed off by the abrasive grain processing. It becomes possible to obtain the probe highly stable in shape.
Furthermore, it is preferable that the oscillating means includes a piezoelectric member supporting the probe. This provides a stable arrangement for supporting the probe stably.
Furthermore, it is preferable that the oscillating means includes a piezoelectric member provided on the probe. This is effective to simplify the probe arrangement.
Furthermore, it is preferable that the distortion detecting means includes a piezoelectric member provided on the probe. With this arrangement, it becomes possible to measure the oscillating condition of the probe at the position where the oscillatory distortion is maximized. The oscillating condition can be measured with high accuracy.
Furthermore, it is preferable that the distortion detecting means includes a strain gauge provided on the probe.
Furthermore, it is preferable that the displacement of the probe is adjustable so as to stabilize a phase variation and/or an amplitude variation based on the comparison between a signal obtained from the distortion detecting means and a drive signal of the oscillating means. This realizes a quick and smooth feedback or servo control for positioning the probe. The stable configuration measurement can be realized.
Furthermore, it is preferable that a voltage is applied between the probe and the objective surface to detect electric characteristics of the objective surface based on a current value measured between the probe and the objective surface.
Furthermore, it is preferable that the probe and the objective surface are magnetic members, and the probe includes a coil to detect the magnetic characteristics of the objective surface based on a magnetic flux density modified in accordance with the oscillation of the probe.
Another aspect of the present invention provides a method for manufacturing a probe comprising the steps of adding a distortion detecting member on a platelike beam material, machining the platelike beam material into a predetermined beam structure, and removing a deteriorated layer from the resultant beam structure. With this manufacturing method, it becomes possible to measure the configuration of the measuring object regardless of its conductiveness without being adversely influenced by the oxide film or dusts on the surface.
Furthermore, it is preferable in the above-described probe manufacturing method that the adding step of the distortion detecting member includes the steps of bonding a piezoelectric member on the platelike beam material and machining the bonded piezoelectric member into a predetermined configuration.
Furthermore, it is preferable in the above-described probe manufacturing method that the adding step of the distortion detecting member on the platelike beam material includes the steps of forming a piezoelectric thin film on the platelike beam material and machining the piezoelectric member into a predetermined configuration during or after the formation of the piezoelectric thin film.
Furthermore, it is preferable in the above-described probe manufacturing method that the machining step of the platelike beam material into the predetermined beam structure is performed by a micro electric discharge machining. It becomes possible to flexibly form the probe in various shape.
Furthermore, it is preferable in the above-described probe manufacturing method that the removing step of the deteriorated layer from the resultant beam structure is performed by the abrasive grain processing.